Properties and Analysis of Gaseous Alternative Fuels II: Fuels Based on Natural Gas and Biogas

Abstract

The importance of alternative energy sources is constantly growing, especially due to the ever-increasing energy consumption of mankind and due to the effort to replace existing sources with more environmentally friendly ones. This article is another in a series of articles focused on an overview of technical requirements and testing methods for alternative gaseous, liquid, and solid fuels. This series of articles aims to provide an overview of the required properties of individual alternative fuels, the possibilities of their analysis, and the significance of individual analyzes. This article provides an overview of the technical requirements prescribed by legislation and relevant standards for automotive fuels based on natural gas (fossil methane) and biomethane. Furthermore, prescribed analytical tests are presented, which have been used to monitor the quality of these fuels. To a lesser extent, the importance of selected analytical tests is also discussed. Natural gas can be compressed or liquefied for use in automobile transport. In the first case, CNG fuel is obtained, and in the second, LNG. As a source of renewable methane or biomethane, biogas can be used, which is produced by anaerobic fermentation of agricultural waste or other raw materials in biogas plants. The obtained biogas can be used for the combined production of heat and energy. Alternatively, it can be purified into biomethane, which can be injected into the natural gas distribution network or used in automobile transport in the form of bio-CNG and bio-LNG. In general, it can be stated that the analysis of fuels based on natural gas and biomethane is well managed. Instrumental equipment and analytical methods used for natural gas analysis can be used to analyze these fuels. The properties of fuels based on natural gas and biomethane are closely related to their composition. In terms of proper operation and performance of the combustion engine, the lower heating value, Wobbe number, and methane number are critical parameters. An important parameter is also the sulfane content, increased content of which can lead to corrosion of engine components. In terms of emissions, the total sulfur content is an important parameter also. Sulfur compounds are undesirable in emissions for environmental reasons. At the same time, they are also catalytic poisons. Other critical parameters of fuels based on natural gas and bio-methane are the water content or dew point of water.